The WHO said that poor air quality increases the risk of stroke, heart disease, lung cancer, and chronic and acute respiratory diseases, including asthma.

Dr Penny Woods, chief executive of the British Lung Foundation, added: “It is deeply concerning that 40 UK towns and cities are failing to meet WHO standards for the smallest, most harmful pollution particles.

“These particles are able to reach deep into our lungs and even into our bloodstream, and can have a serious impact on our breathing and wider health.

“It is clear from this report that the UK is facing an air pollution crisis.

Pollution protesters put gas masks on London monuments:

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“Unfortunately, the Government’s response so far has been inadequate. Swift action must be taken to reduce pollution levels in the UK and protect our lung health.”

The WHO has released data on levels of particulate matter in 3,000 urban areas in 103 countries around the world, highlighting what it described as the “greatest environmental risk to health”.

Pollution is responsible for more than three million premature deaths worldwide ever year and is caused by numerous sources including industry and traffic.

Dr Maria Neira, director of public health at the WHO, said: “Urban air pollution continues to rise at an alarming rate, wreaking havoc on human health.

Poor air quality is a major cause of disease and death (Image: Getty Images)

“At the same time, awareness is rising and more cities are monitoring their air quality. When air quality improves, global respiratory and cardiovascular-related illnesses decrease.”